Resilient contacts for use in weakcurrent apparatus



Aug. 13, 1957 WEUER ET AL 2,802,923

RESILIENT CONTACTS FOR USE IN WEAK-CURRENTAPPARATUS Filed March-29, 195s STAINLESS STEEL WITH NICKEL COATING NICKEL OR STAINLESS STEEL WITH NICKEL COATING INVE'NTORS BEREND WEIJER JANNES DRAIJER LESLIE CLAUDE BALL RESILIENT CQNT ACTS FOR USE IN WEAK- CURRENT APPARATUS Berend Weijer, Jannes Draijer, and Leslie Claude Ball,

Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application March 29, 1955, Serial No. 497,774

Claims priority, application Netherlands March 31, 1954 2 Claims. (Cl. 200-166) The invention relates to resilient contacts for use in weak-current apparatus, such as amplifiers, radio and television receivers.

In practice the said resilient contacts have to satisfy the requirements, that they have constant and low contactresistances are wear-resistant and adapted to be soldered. An even more important requirement is that the contact does not give rise to phenomena which inradio or television receivers cause so-called crackling. These requirements must be satisfied even after frequent use and if the contacts are exposed for long periods of time to an atmosphere containing hydrogen sulphide, sulphur dioxide or salt.

Resilient contacts are known one part of which consists of silver-plated copper whilst the other part consists of Phosphor-bronze coated with a silver layer. These contacts have a limitation in that in course of time sulphide settles on the silver and causes crackling. Therefore it has been suggested to replace the silver by other metals, such as rhodium, gold, palladium or combinations or alloys of these metals. Thus, a considerable improvement is indeed obtained, but the last-mentioned metals are expensive and consequently not very suited for use in apparatus the cost of manufacturing of which would thus be determined to a considerable extent by the price of the used noble metals.

In experiments performed prior to arriving at the present invention a large number of resilient contacts made of different metals were examined inter alia concerning the production of crackling noise, Wear resistance, solderability and conductivity. After pauses of many hours the contacts were opened and closed a few hundred times. During the pauses the contacts were exposed to an atmosphere containing in addition to other constituents hydrogen sulphide or sulphur dioxide. In order to measure the contact resistance a voltage of a few microvolts was applied to the contacts and the phenomena produced were recorded after having been amplified a thousand times. The examined materials are listed in the following table.

Resilient contact part Non-resilient contact part Phosphor-bronze Copper Phosphor-bronze-l-lO Ni Copper+ln Ni Plnlslphor-bronze 2014 Cu 2n Phosphor-bronze+20n Ag+2u Or Phosphor-bronze+0.5 Rh

Phosphor-bronze+20 Ou+2n Cr Plzfsphor-bronze hard silvered Gopper+Ag (plated)+0.5 .s Gr Copper+ 0.25 4 Rh Oopper+0.5n Or Copper+Ag (plated) u)- Phosphor-bronze+1n Au Copper-+1 Au Phos hor-bronze+8 Ag-l-lp. Au Copper Ag (plated)+1 Au stami' ess steel stainless steel atent G "ice None of the resilient contacts of the kind enumerated in the table gave satisfactory results during tests.

It was surprising to find in prolonged experiments that a resilient contact the resilient part of which consisted 5. of stainless steel coated with nickel and the other part of which was either built up similarly or consisted of solid nickel satisfied all the above-mentioned requirements. In addition, it was found that these contacts needed no lubrication.

According to the invention, shown in the single figure of the drawing, resilient contacts for use in weak-current apparatus are composed of two parts, one of which consists of stainless steel coated with nickel Whilst the other consists either of nickel or of nickel coated on stainless steel, nickel being the contact metal. 7

In prolonged experiment it was found that the stainless steel cannot be replaced by other materials, such as, for example, iron or normal steel or Phosphor-bronze so that the contacts satisfy practicalrequirements. Consequently, the invention does not relate to other metals than stainless steel. The term stainless steel as used herein is to be understood to mean chromium-nickel-iron alloys, preferably an alloy containing in addition to iron 18% of chromium and 8% of nickel.

Very good results were obtained with the use of thin nickel layers of from 2 to 20 Nickel can be coated on stainless steel in various manners, for example by plating. In a preferred embodiment of the invention the nickel is deposited on the steel by electro-deposition. This may be done in the following manner.

Components for resilient contacts made of 18-8 chromium-nickel steel are degreased by means of trichlorethylene and subsequently by means of a hot solution of caustic soda. Thereupon the components are pickled with the use of hot concentrated hydrochloric acid and Washed with water. Then the articles are activated anodically for a short period of time by treating them in a bath of concentrated hydrochloric acid which is saturated with nickel chloride so that the surface is coated with a very thin nickel layer. The nickel bath is then replaced by another bath containing 240 g. of nickel sulphate, 40 g. of nickel chloride and 30 g. of boric acid per litre. In this bath the components are connected as the cathode and thus coated with a nickel layer 1011. thick.

The resilient contacts in accordance with the invention have proved to be particularly suited for use in so-called wave switches for use in radio and television receivers.

What is claimed is:

1. A resilient contact of the class described comprising at least two parts, one part constituted of stainless steel coated with nickel and the other part constituted of nickel, the nickel being the contact metal.

2. A resilient contact of the class described comprising at least two parts, one part being of stainless steel constituted of 18% chromium, 8% nickel and the remainder of iron and coated with nickel, and the other part being nickel, said nickel layer being deposited on said stainless steel by electro-deposition and being from between 2 to 20 thick.

References Cited in the file of this patent UNITED STATES PATENTS 883,554 Maillard Mar. 31, 1908 1,925,856 Vaughan Sept. 5, 1933 2,547,947 Kleis et a1 Apr. 10, 1951 

3. A RESILIENT CONTACT OF THE CLASS DESCRIBED COMPRISING AT LEAST TWO PARTS, ONE PART CONSTITUTED OF STAINLESS STEEL COATED WTIH NICKEL AND THE OTHER PART CONSTITUTED OF NICKEL THE NICKEL BEING THE CONTACT METAL. 